ULTRACENTRIFUGATION Flashcards

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1
Q

what is cell fractionation

A

process where cells are broken up and the different organelles they contain are separated
helps with the study of cell structure and function

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2
Q

what are the 2 stages of cell fractionation

A

homogenation
ultracentrifugation

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3
Q

why a cold buffered isotonic solution

A

cold - reduce enzyme activity which may break down organelles
isotonic - prevents organelles bursting / shrinking due to gain / loss of water
buffered - maintain a constant pH to prevent damage to organelles

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4
Q

what is an ultracentrifuge

A

refrigerated low pressure chamber with a rotor
rotor speed can be changed slowly

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5
Q

steps of cell fractionation

A
  1. tissue minced and placed in a cold, isotonic, buffered solution
  2. a homogeniser grounds it into smaller pieces releasing the organelles from the cell membrane
  3. the homogenate is filtered removing complete cells and large debris
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6
Q

stages of ultracentrifugation

A
  1. a suspension of homogenate is placed in a test tube and centrifuged
  2. slower speeds - large fragments (sediment pellets0 collect a the bottom and small fragments remained at the top suspended in the supernatant liquid
  3. sediment pellets are removed and the remaining supernatant is respun at a faster speed at greater force. some of the smaller fragments collect at the bottom forming a new pellet
  4. smaller and smaller fragments can be recovered
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7
Q

what is differential centrifugation

A

process involving centrifuging at different speeds
organelle sizes are relatively constant and seem to seperate at specific speeds

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8
Q

process of differential centrifugation

A

when the centrifuge spins, the centrifugal force causes pellets of the densest organelles to form at the bottom
the centrifuge is first spun at a low speed and then the process is repeated with increasing speeds
each time, the supernatant is moved, leaving behind a pellet of organelles

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9
Q
A
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